Using cutting-edge audio technology, Secret World of Sound with David Attenborough is a ground-breaking series that explores the many incredible ways that animals hear and produce sound – and how this influences the decisions they make.
Immerse yourself in the Secret World of Sound with a selection of spectacular photographs taken during the making of the series, then step behind the scenes with series producer Sharmila Choudhury as she reveals why sound was chosen as the focal point of the wildlife documentary, how an ugly fish stole her heart, and what it's like to work alongside Sir David Attenborough.
Secret World of Sound: Behind-to-scenes
Photographs by Humble Bee Films
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The making of Secret World of Sound with series producer Sharmila Choudhury
What was the genesis of this idea?
Natural history films are known for their stunning visuals but the sounds tend to play a secondary role, often overshadowed by music. In this series, we had the idea that we wanted to place sound centre stage, both in terms of recording all the sounds the animals make, but also the sounds of the environment that they live in. In natural history films, the sound is often added afterwards from sound libraries, so they aren’t always recordings of those animals when they’re being filmed. Sound technology has evolved massively over the last few decades, partly for the music industry and for the gaming industry, so the recording devices and microphones that you get now are phenomenal.
Using the most up-to-date equipment, the idea behind the series was to look at how animals use sound in the natural world. From a storytelling point of view, we wanted to ask, how do animals produce sound and why do they do it? And it turns out that it’s crucial in the lives of most animals. It helps them to survive, to hunt for food, to attract prey or to avoid being eaten themselves. They use sound to find a mate and to raise their offsprings and for all kinds of communication.
"Natural history films are known for their stunning visuals but the sounds tend to play a secondary role, often overshadowed by music. In this series, we had the idea that we wanted to place sound centre stage."
What sort of sounds do you focus on during the three episodes?
There are a lot of sounds in the natural world including sounds that we can’t actually hear: insects, for example, don’t have ears like we do, so they can’t hear sounds that travel through the air, but they have very fine sensory hairs on their legs and feet which allow them to pick up sound as vibrations. If you walk into a jungle there will be all these insects talking to each other, singing to each other, but we can’t hear any of that, so part of the aim of this series to make some of those sounds audible to us.
Humans can only hear sounds within a fixed frequency range: a lot of bats and dolphins make sounds that are higher pitched or, in the case of elephants, lower pitched than we can hear. Those sounds were long beyond the scope of our understanding and it’s only recently that scientists have started to try to work out what they mean. As much as we could, we’ve tried to bring the latest science and understanding into this series.
How valuable is the preparation and research that you do in your planning of a series like this?
Most natural history films are underpinned by the latest research, and often scientists in the field help, but even more so for this series. We used everything from a tiny, tiny microchip microphone the size of your little fingernail that you can insert into a beehive or into a bird’s nest, to specialist microphones that you can put into water called hydrophones that are so sensitive, they can pick up how fish talk to each other. That blew my mind: virtually all fish talk to each other!
There were also a couple of technologies that we used which weren’t made for our industry, which we then adapted to allow us to record animal sounds. We worked closely with the engineers of those devices, two in particular: the acoustic camera and the laser vibrometer. That was a crucial breakthrough for us as filmmakers.
"It blew my mind: virtually all fish talk to each other!"
Can you expand a bit more on that?
The acoustic camera was developed for the gas industry to detect gas leaks. It’s a small camera surrounded by sixty really sensitive microphones that can pick up and locate even the faintest sound. They point this device at gas pipes and the microphones impose a kind of thermal image onto the camera and show you with a red hot dot where the sound is coming from. As you get further away from the sound, the colours change. We thought that would be good for trying to find animals using sound that we can’t normally hear or locate.
We used it for three sequences in the series: one was to show how great grey owls hunt voles under the snow. It’s a very classic natural history sequence that has been filmed before but ordinarily you have to guess what the owl is hearing: with this camera, we could point it at the bit of snow where the owl is looking and we could actually see the voles scuffling under the snow, which is the tiniest sound of little feet and squeaks. So, it was a great piece of kit, but we had to adapt it because the camera itself wasn’t broadcast quality, not even HD. We had to design a special rig where the acoustic camera sat side by side with one of our broadcast cameras, as close as possible, filming the same thing at the same time. Then we could overlay the image produced by the acoustic camera onto our broadcast quality image.
"From a storytelling point of view, we wanted to ask, how do animals produce sound and why do they do it? And it turns out that it’s crucial in the lives of most animals."
The other sequence we’ve used it on, which I think is the most exciting, was an event that occurs in the Arizona desert where the rains trigger an explosive breeding of all the frogs in the area for just a couple of days. The frogs all pile into these one or two ponds which have just formed and there will be a number of species all calling for mates. But they all look pretty much the same, green or brown frogs, so how do you find your own type of male or female in this crowd of everybody shouting away? The answer is they do it with sound: they all pick a slightly different frequency and way of calling. With our ears we can’t pick that detail out in the cacophony, but the acoustic camera allowed us to record different frequencies in different colours so you can actually see the different species. That was extraordinary.
Once you had the technology in place, how did you choose the stories?
So much has been filmed before that the challenge is always to try and let the audience see the natural world through a different lens. In this series the aim was to show it through the lens of sound. If you go out into nature or a walk in a woodland, I think it will be the sounds that strike you as much as anything else: the birds singing, or in a rainforest monkeys howling.
In nature, every single sound has a purpose, and it’s evolved for a reason. I think we tend to forget that there’s a reason why most birds sing in spring - they’re all looking for a mate – and they sing first thing in the morning because that’s the time of day where sound carries the best due to the temperature of the air. I think, whichever story we chose, it needed to shed a light on the importance of sound in the natural world.
What are some of your favourite stories?
One of my favourites is the one about the plainfin midshipman. It’s a pretty ugly fish but it’s a fabulous story and it’s quite hard these days to find stories that no one has filmed before. We knew that the male fish make this extraordinary hum as a courtship song to lure the females out of the deep, but we didn’t know if we could film it. This fish lives really quite deep down in the Pacific Ocean most of the year, below three hundred metres, and it only comes up into the shallows once a year.
It’s the most extraordinary animal, and yet it’s not a big fish; thirty centimetres or so, but they produce this hum which is phenomenally loud – one hundred and ten decibels, which is as loud as a lion’s roar. For decades the local people had no idea where the sound was coming from. They thought maybe it was produced by Navy submarines or something similar: the noise was so loud it actually kept them up at night. It’s quite a haunting, eerie sound so I wonder what people made of it in centuries past: maybe they thought it was some sort of God or monster.
We had planned to film most of this courtship song in a tank set-up, but we also sent a cameraman to try and get us something in the wild: because nobody had tried it before, we didn’t know how difficult or easy it would be. Surprisingly, he got the whole sequence in the wild naturally which is fantastic.
"We knew that the male fish make this extraordinary hum as a courtship song to lure the females out of the deep, but we didn’t know if we could film it."
Another one that people will enjoy is the elephants in Kenya.
Yes. Elephants are amazing because they’ve got massive ears and good hearing through the air, but their feet have special sensors which are even better at picking up sound, particularly low frequency sounds which travel as a vibration to the ground. By lifting one foot a little bit, they basically exert more pressure on the other one, so it’s even more tightly knitted to the ground. I don’t think I’d ever seen elephants do this before. In our film we have the matriarch in a drought picking up one foot to work out where the noise of the thunder and rains are coming from so she could go and find water. These sounds travel for hundreds of kilometres and will be quite faint by the time they hit the elephant, so all the herd stand completely still so she can detect those sound waves which will travel up her body and into her ear bones. Elephants also use their feet to detect the rumbles from other elephant herds; they can communicate with each other over long distances using these low frequencies.
Can you talk a little about the sequence with the gulls and the earthworms in Vancouver?
That was an interesting sequence because we thought it would be a fun and easy one to do. You may have seen gulls doing this strange foot-paddling dance at times, even in cities; it’s a behaviour that has a purpose of tricking worms up to the surface because apparently it may mimic the sound of raindrops. Then, of course, the gulls can eat them. If you asked me which of our sounds was the hardest to record, I would probably say the gulls foot-paddling because it’s actually a very quiet sound and you have to get quite close to them. No-one had ever tried to record it before.
First we tried dotting tiny microphones around a patch of grass hoping the gulls would do the paddling there but we just could not get close enough to them. Then we tried the most powerful microphones that are directional, and we pointed them at the gulls, but that didn’t work either. There was always some interfering noise that was louder, because this behaviour tends to happen in cities with traffic. We had the whole office out for weeks and we just couldn’t get it! In the end the only way we were able to record the sound was in a gull sanctuary where we placed small microphones under the turf and waited, and eventually they did it in the right spot. But that was hard.
"If you asked me which of our sounds was the hardest to record, I would probably say the gulls foot-paddling because it’s actually a very quiet sound and you have to get quite close to them."
What was the biggest challenge making this series?
Without a doubt: climate change. It’s something we’ve seen creep in for a number of years now; an increasing number of shoots are affected by unpredictable weather patterns. For natural history filming, we do a lot of very precise research to know that when we go out somewhere, the animal is going to be there, and it’s going to be doing the thing it’s supposed to be doing, but because climate change has messed around with the seasons so much, very often we arrive and the scientist or local fixer will say “Well, this has never happened before, they’ve been coming here for forty years and they’re just not here this year.” That might have affected one or two shoots in the past but every single shoot on this series was affected by climate change in a major way.
For the caiman sequence, there was virtually a complete failure of breeding. We just about managed to find enough nests that we could film the story. The worst affected shoot was the elephant filming in Kenya, which shocked both us and the scientists. We filmed in Amboseli National Park, where I’d been before, so I knew it should be lush and green and that the elephants should be joyous and socialising with each other and communicating, greeting each other with trumpeting and excitement as they come together. But they’d had such a bad drought for the last two years that the elephants were starved and desperate. Every night they’d go into the surrounding fields to feed, and every morning they would come back into the national park where there was a small swamp for drinking water. They’d be walking in a single line, heads down, not making a single sound. We wanted to film more elephant behaviour to do with sound and communication but because they were so stressed by the climate and lack of food, they had stopped all communication because that takes energy. The scientists said they they’ve never seen anything like it: I think on a single day we heard maybe four or five rumbles all day when normally there’d be hundreds. Climate change is so stark out there now, it’s shocking.
"We wanted to film more elephant behaviour to do with sound and communication but because they were so stressed by the climate and lack of food, they had stopped all communication because that takes energy."
Did you weave that conservation message into the series?
The main focus of the series was always to be about the sounds that animals make, whether it’s to find a mate or for survival. But there were clearly animals we encountered which had been impacted by environmental issues, so we tried to weave these stories in where we could and where it was related to sound.
For the episode with the coral reef sequence, we also made the behind-the-scenes piece at the end more overtly about climate change. It’s a short series, three parts, so there were many stories we couldn’t feature, and it was difficult to find the right balance. The series is primarily about exploring the sounds of nature and so any environmental messages had to sit comfortably within, but I hope we’ve achieved that.
Will you look at sound in a different way for your future projects, now that you know the possibilities?
I hope we will. It’s a huge effort to record all the sounds like we did, and we had to have a dedicated specialist sound recordist on every single shoot. You often can’t record the sound at exactly the same time as you’re filming the animal because the film cameras and crew make a lot of noise moving around, so it’s not easy. But I hope others will watch this series and feel that it’s worth, at least sometimes, focussing more on the natural sounds. Most natural history films rely quite heavily on music, which can add drama and emotion to a story, but music can also distance you from a scene a little bit. I personally love hearing more of the natural sounds. I find it beautiful, immersive and more real – I feel like I’m there. Again, it’s a balance.
" I personally love hearing more of the natural sounds. I find it beautiful, immersive and more real – I feel like I’m there."
What was it like working with Sir David Attenborough?
It’s always a privilege to work with David. He is always so enthusiastic and interested in the subject matter, and he particularly likes stories that are slightly different and shed a new light on things. For that reason this series certainly appealed to him. We shot a scene of him walking through a woodland in spring to illustrate the beauty of bird song and we were obviously delighted he wanted to do that. That was filmed in the Wye Valley where we filmed the white throated dippers at the same time. That was one of the loveliest shoots and I think the dipper is one of those birds that is often overlooked.
I have never heard them sing and the reason is because their song is often masked by the sound of the streams. It was really only when we stripped away the sound of the water that this song was suddenly revealed and all of us on the team were gobsmacked by how beautiful that song is: it rivals a nightingale and every dipper sings a different song, and they never sing the same song twice. They’re brilliant composers, they just keep changing
the notes on the compositions. I think it’s also one of David’s favourite sequences; we wanted to do a piece with him and a dipper, and his enthusiasm at 97 to still want to get the shot right and get into the right position is amazing. He crawled through the grass on his hands and knees to be there at eye level with the dippers so we could get the shot of him and the little bird in the foreground, which was just extraordinary.
You also had him in a rowing boat and feeding a starling ...
He’s quite remarkable: still full of energy, very passionate about telling a good story, and always completely engaged with the subject matter. It was a real privilege and a huge amount of fun working with him on this series.
Photographs by Humble Bee Films